Sensei no Ojikan: Doki Doki School Hours

Description:

Meet Suzuki Mika, teacher at Okitsu High School. Mika-sensei is a good teacher, but she has a small problem... literally. Although she's 27, she is only 148 cm tall, and has the face of a child. As a result, it is often difficult for Mika-sensei to get anyone to take her seriously.
(Source: ANN)